Distributed ad hoc mesh network protocol for underground mine and hazardous area communications

ABSTRACT

Methods and apparatus for forming and maintaining an ad hoc mesh network suitable for reliable voice and data communications in underground, industrial and other hazardous environments. This invention includes support for cooperative negotiation of dedicated transmission bandwidth for all fixed network nodes, determination of network time synchronization without a pre-determined time master, discovery and merging of adjacent ad hoc mesh networks, and routing techniques for voice, data and network status packets which react instantaneously to network topology changes. Furthermore this invention provides a reliable communication network for mobile nodes carried by personnel and sensor nodes that are fixed or mobile that supports voice, data and tracking/situation awareness. A current application for this technology is a coal mine communication system with an operations center to dispatch, monitor and control coal mine operation including communication and location of mine personnel, and environmental conditions in the mine.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Stage application of InternationalApplication No. PCT/US2009/037755, filed Mar. 20, 2009, the disclosureof which is hereby incorporated by reference herein in its entirety.

TECHNICAL FIELD

The present invention relates to a data protocol to implement a wirelessvoice and data communication system that for use in underground andhazardous areas for dispatch, remote supervision, and tracking ofpersonnel, as well as, monitoring, asset control, and management ofwireless sensors and equipment. More specifically the protocol enablesthe creation of a wireless ad hoc mesh network and facilitates thetransport of communication packets for voice, data, text and networkoperations supporting normal and emergency operation.

BACKGROUND OF THE INVENTION

Recent events have indicated the need for reliable communication systemsduring emergencies in underground and hazardous work areas such as coalmines. During a mine disaster the current voice and data communicationsystems fail or shutdown so the conditions of personnel, environment andequipment is unknown which complicate recovery efforts. Past miningaccidents have demonstrated that current communication systems are notsufficient to provide the support required to effectively handleevacuation and rescue operations. The 2006 MINER Act amends the FederalMine safety and Health Act of 1977 stating underground coal mineoperators must provide for post accident communication betweenunderground and surface personnel via a wireless two-way medium withinthree years. Robust and reliable mine communications are critical forboth mining operations and in the event of a mine emergency. TheNational Institute for Occupational Safety and Health (NIOSH) released asolicitation in late 2006 for an underground communication system thatis highly reliable and provides in-mine and mine-to-surface voice anddata communications to evaluate wireless mesh network technology as partof an underground communications system.

Prior art mesh communications systems for use in hazardous environmentshave used the standard Institute of Electrical and Electronics Engineers(IEEE) 802.11 wireless protocol to transfer status and multimediainformation as well as centrally generated and controlled routing tablesto control packet latency in a multi-cast application with a changingnetwork topography. The IEEE802.11 wireless protocol supports aninfrastructure mode in which mobile nodes are connected to acoordinating master referred to as the Access Point (AP) and an ad hocmode in which mobile nodes form peer-to-peer connections with nopreconfigured network topology. The original 802.11 protocol had verylimited Quality of Service (QoS) mechanisms. A Point CoordinationFunction (PCF) was specified in which each AP sends a poll to eachclient one at a time to provide a contention-free transmissionopportunity. This media access control (MAC) method has not beenimplemented in many APs and is bandwidth inefficient since it alwaysrequires a poll packet be sent to the client for each high prioritypacket to be sent to the AP. The 802.11e amendment was incorporated intothe 802.11 standard in 2007. It specifies two additional mandatory QoSMAC methods. The first method is the Enhanced Distributed Channel Access(EDCA) method which specifies traffic priority levels and assignedtransmission opportunities for each priority level. This method doesprotect against collisions (and subsequent loss) of high-prioritypackets due to low-priority packets, however it does not protect againstcollisions of packets with the same priority from multiple clients. Thesecond QoS method introduced by 802.11e is an infrastructure-only methodreferred to as Hybrid Coordinator Function Controlled Channel Access(HCCA). This QoS method is similar to the PCF method with the exceptionsof the timing of the contention-free transmission opportunities is notlimited to certain inter-beacon time slots and the AP is able to poll aclient for a particular Traffic Class (TC) to enable session-aware QoS.This HCCA method suffers from the same bandwidth inefficiency as PCF. Inaddition to the lack of an efficient method to guarantee transmissionopportunities for high priority packets between a client and an AP(infrastructure mode) or between two clients (ad hoc mode), the 802.11solutions do not provide the additional necessary capability to forwardsaid packet to the next destination in the network in an efficient andcontention-free manner. Therefore, what is needed is a method andapparatus for establishing dedicated transmission opportunities for eachfixed node in a given cluster to forward packets to the next node in thecluster as well as contention-based transmission opportunities for fixednodes and mobile nodes to join the cluster.

Furthermore, the efficient routing of packets across a mesh network is avital component in determining the packet latency through the network.Prior art mesh network communication systems for hazardous environmentshave utilized routing tables generated from a centralized location andperiodically propagated across the network using high priority MACmessage mechanisms, resulting in a delay in routes being modified asconditions change. There is also a need in the art for an intelligentde-centralized flood routing technique to ensure mobile units canseamlessly roam throughout the network.

SUMMARY OF INVENTION

This invention relates to a computer-implemented method for providing aprotocol enabling reliable communications between elements of an ad hocmesh network which include at least fixed mesh nodes, mobile mesh radionodes and gateway nodes. One of the fixed mesh nodes is designated atime master node, and an intelligent de-centralized flood routingtechnique is used to ensure that units containing mobile mesh radionodes can seamlessly roam throughout the network. Each fixed mesh nodetransmits over a pair of bonded, time-synchronized channels, one ofwhich is a voice channel while the other is a data channel.

The protocol includes at least one super-frame time interval. If thereis more than one super-frame time interval, they are all of equalduration and synchronized with the time master node. There are at leasttwo time slots within the primary level of each super-frame, one ofwhich is assigned to be a first level contention access period time slotand the second of which is assigned to be a period during which fixedmesh nodes may transmit network packets to neighboring fixed mesh nodesand to any mobile mesh radio nodes with which they are associated. Theprotocol has multiple levels of time slots, each of which is assigned toa specified type of activity to account for the various functions to beprovided by the protocol.

BRIEF DESCRIPTION OF DRAWINGS

The foregoing and other objects, aspects and advantages of the inventionwill be better understood from the following detailed description of theinvention with reference to the drawings, in which

FIG. 1 illustrates the concept of a wireless voice and data ad hoc meshnetwork deployment in a logical design block diagram view according toan embodiment of the present invention.

FIG. 2 illustrates an example of a cluster of Fixed Mesh Nodes,depicting the parent-child relationships as well as the transceiveroperation during a typical protocol super-frame.

FIG. 3 illustrates the partitioning of a protocol super-frame into firstlevel time slots as defined by this invention.

FIG. 4 illustrates the partitioning of a first level FMN-to-FMN timeslot into second level time slots as defined by this invention.

FIG. 5 illustrates the partitioning of a first level Data ChannelContention Access Period (CAP) time slot into second and third leveltime slots as defined by this invention.

FIG. 6 illustrates the partitioning of a first level Voice ChannelContention Access Period (CAP) time slot into second and third leveltime slots as defined by this invention.

FIG. 7 illustrates the partitioning of a generic first level frame intosecond and third level frames as defined by this invention.

FIG. 8 illustrates the partitioning of a third level Frame Control Fieldframe into fourth level frames as defined by this invention.

FIG. 9 illustrates the partitioning of a third level Extended Headerframe into fourth level frames as defined by this invention.

FIG. 10 illustrates the partitioning of a generic fourth level ExtendedHeader frame into fifth level frames as defined by this invention.

FIG. 11 illustrates the partitioning of a fourth level Slot InfoExtended Header frame into fifth level and sixth level frames as definedby this invention.

FIG. 12 illustrates the partitioning of a sixth level Cycle Slot#/Foster Rotation frame of a fourth level Slot Info Extended Headerframe into seventh level frames as defined by this invention.

FIG. 13 illustrates the partitioning of a fourth level PiggybackAcknowledge (ACK) Extended Header frame into fifth level and sixth levelframes as defined by this invention.

FIG. 14 illustrates the partitioning of a fourth level Piggyback GrantExtended Header frame into fifth level and sixth level frames as definedby this invention.

FIG. 15 illustrates the partitioning of a fourth level Future GrantExtended Header frame into fifth and sixth level frames as defined bythis invention.

FIG. 16 illustrates the partitioning of a first level Single Data FramePacket into second level, third level and fourth level frames as definedby this invention.

FIG. 17 illustrates the partitioning of a first level Concatenated DataFrame Packet into second level, third level and fourth level frames asdefined by this invention.

FIG. 18 illustrates the partitioning of a first level SYNC MAC frameinto second level, third level and fourth level frames as defined bythis invention.

DETAILED DESCRIPTION OF THE INVENTION

This invention helps to provide reliable voice and data communicationswith personnel and sensors within a hazardous area and also with aremote operation center during normal operations as well as during anevent that requires shut down of normal operations. The invention allowsrescue teams to determine personnel status, where personnel are located,and environment conditions such as water, toxic gases, and oxygenavailability in the hazardous area. The wireless voice/data networkprotocol of the present invention comprises a number ofintercommunicating blocks which automatically form a Wireless MeshNetwork (WMN) 100 that can reform when links are removed or blocked.

The system and method of the present invention provide a voice/datanetwork protocol to supply Operations Center staff with event detectioninformation, voice and text communications, and personnel locationinformation, as illustrated in FIG. 1. In a preferred embodiment, fourtypes of nodes are provided in the network:

Fixed Mesh Node FMN 102 is a stationary dual-transceiver mesh radio unitoperates on the WMN 100. Multiple units operate together to form thesemi-static infrastructure for the WMN 100. Each FMN 102 has thecapability to coordinate individual clusters within the wireless meshnetwork WMN 100 and route data through the network between mobile nodesand to a Gateway Node (GWN) 104. An FMN 102 can also communicate througha wired backbone headend 106 with a wired backbone 107, such as a leakyfeeder system, as well as form the core links for WMN 100.

GWN 104 supports the transfer of information between WMN 100 and theinfrastructure for a wide area network (WAN). GWN 104 is a highlymodular design that is normally implemented as a fixed device but couldbe a mobile device. GWN 104 includes all of the functions of a fullfunction FMN 102.

Mobile Mesh Radio (MMR) 101 is a portable device carried by personnelthat allows them to have voice and data communication with a NetworkOperations Center 105 and/or other personnel equipped with an MMR 101.MMR 101 can also be a relay link between another MMR 101 and an FMN 102,or between a sensor mesh node (SMN) 103 and an FMN 102.

SMN 103 connects data from various types of sensors such as light,noxious gas, acoustic, temperature, oxygen, and imaging sensors into WMN100 by communicating through one or more FMNs 102 or one or more MMRs101 to forward information from a sensor to network operations center(NOC) 105.

Other units may also be added to WMN 100. For example, a Data Mesh Nodemay be used to communicate with equipment operating in a mine orhazardous area. Thus, use of this invention is not limited to the typesof nodes specifically mentioned.

1. Definitions

The following terms are used throughout this description with thefollowing meanings:

Node—This term is used to denote a Fixed Mesh Node (FMN) 102, GatewayNode (GWN) 104, Mobile Mesh Radio (MMR) 101 or Sensor Mesh Node (SMN)103.

Time Master—This term refers to the node which is providing the protocolsuper-frame timing to all the other nodes in a cluster. This node mayhave direct children nodes and if it does it may have inherited childrenthrough these children. Its direct children of the Time Master willdirectly synchronize to the time master's slot timing while theinherited children will synchronize to their respective parents slottiming thus inheriting the time master's timing with some offset due topropagation delay. For example, in FIG. 2, Node 1 is the Time Master;Node 2 is the only direct child of Node 1 while Nodes 3 and 4 are theinherited children of Node 1 through Node 2.

Cluster—A cluster is a group of nodes which all have the same timemaster. Nodes in a cluster do not necessarily (and often will not) havedirect RF connectivity to all the other nodes in the cluster.Information packets between clusters pass through a pair of gateways ifa gateway exists in each cluster. FIG. 2 illustrates a cluster of FMN'scontaining nodes 1, 2, 3 and 4.

Parent Node—A parent node is a node which is providing a time referenceto a child node. In FIG. 2, a parent-child relationship is illustratedby the lines towards which indicator 205 points in which the arrowheadfor each of the lines points towards that node's parent. Thus, node 1 isthe parent of node 2 while node 2 is the parent of node 3 and node 4.The numbering system for the nodes is described in further detail below.

Child Node—A child node is a node which is basing its time reference ona parent node. The only node in a cluster which is not a child to someparent is the time master.

Peer Node—A peer node is a node which has the same time reference as agiven node but is not a child or parent of that node. In FIG. 2, a peerrelationship is illustrated by a line without arrowheads, such as line210.

Observing Node—A node which is examining the frequency spectrum foradjacent nodes, parent node, children nodes, peer nodes, and knownnodes.

Known Node—A node is said to be a known node to an observing node if itspresence is known by the observing node but it is not in the samecluster as the observing node.

Neighbor—A node is considered to be a neighbor of another node if it isthe parent, a child or a peer to that node. Known nodes are notconsidered to be neighbors.

Orphan Node—An orphan node is a node which is currently operating in adedicated search mode. In this mode it will continually search for anynode with a higher time master ranking than it has itself.

Orphan Cluster—An orphan cluster is a cluster which does not contain agateway.

Wireless Mesh Network (WMN) 100—Refers to the mesh network in itsentirety, including FMNs 102, GWNs 104, MMRs 101 and SMNs 103

2. Functional Overview

The mesh protocol provides a means to form and maintain the fixednetwork (FMNs 102 and GWNs 104) and provides access into the network formobile nodes (MMRs 101 and SMNs 103). The fundamental purpose of thisnetwork is to transmit application layer packets between various pointsin the system with the highest reliability and lowest latency which canbe achieved given a certain system cost.

Since a GWN 104 operates as a mesh network member in a manner which isindistinguishable from an FMN 102 on the mesh radio side, the term FMN102 will be used in the remainder of this description when referencingfunctionality common to both FMN 102 and GWN 104.

3. Frequency and Slot Assignment

An important aspect of this invention is the ability to form a meshnetwork which can provide dedicated bandwidth for each FMN 102 within acluster. This dedicated bandwidth is essential in the efficient routingof voice communications which is very sensitive to any system latency.When an FMN 102 attempts to join an existing cluster of FMN's 102 itsends an Association Request to the FMN 102 which it has determined tobe its best parent. The potential parent responds with an AssociationResponse indicating whether it accepts or rejects the joining FMN 102 asa child. In the case of the former, the parent FMN 102 provides achannel and slot assignment on which the joining FMN 102 is to operate.In this way the bandwidth within a cluster can be managed such that,within a given RF collision domain, each cluster member has a unique RFchannel/time slot combination for it to transmit its FMN-to-FMN messagesin time slots 310 within super-frame 305, shown in FIG. 3.

4. Mesh Operation

FIG. 2 illustrates the operation of a small mesh consisting of 4 nodes.For purposes of this description each node is referenced by its ID, i.e.Node 1 is the node with an ID of 1. Each node has a frequency pairassociated with it, one for the primary channel and one for thesecondary channel. This frequency pair is “bonded” since there is afixed relationship between them and if one is known, the other can beeasily derived. For example, Node 3 in FIG. 2 operates with a primaryfrequency of f₇ and a secondary frequency of f₇′. Each node learns thefrequency pair associated with each of its neighbors during clusterformation.

In addition each node has a first level FMN-to-FMN time slot 310associated with it. For example Node 4 in FIG. 2 has time slot 0associated with it. The time slot for each member of a cluster isassigned during cluster formation.

As illustrated in FIG. 2, during a typical super-frame, each node willtune its primary and secondary transceiver frequencies to its assignedfrequencies during its assigned first level FMN-to-FMN time slot 310 andtransmit any packets it has queued for transmission on that channel asdescribed previously. In addition, during a typical super-frame, foreach first level FMN-to-FMN time slot 310 which is assigned to aneighbor, a node will tune its transceivers to the frequenciesassociated with that neighbor and attempt to receive packets from thatneighbor. Also during a typical super-frame, each node will tune itstransceivers to its assigned frequencies during the first levelcontention access period (CAP) time slot 315, shown in FIG. 3 andexplained further below, attempting to receive packets from transmittingmobile nodes or other FMNs 102 which are attempting to join the cluster.Finally, during any first level FMN-to-FMN time slot 310 which is notcurrently assigned to a neighbor, a node will use both transceivers toscan for other clusters which might provide an improved time metric.

Exceptions to this typical super-frame operation are made in order toallow nodes to discover other nodes associated with other clusters whenthese other nodes are operating in time slots which overlap the timeslots assigned to discovering node or the discovering node's neighbors.These exceptions are known as puncturing events. A node willperiodically puncture its own first level FMN-to-FMN time slot 310, aswell as its neighbors' assigned time slot(s) and the first level CAPtime slot 315. During a puncturing event, the node performing thepuncturing will replace the typical operation described in the precedingparagraph with a scan operation. The puncturing schedule for the twotransceivers for a given node is independent.

5. Routing

In order to support multicast communications, seamless mobility formobile nodes such as MMRs 101 and SMNs 103 and redundant communicationslinks, the routing of voice packets through the mesh network must bedynamic. This invention accomplishes this using an intelligent floodrouting technique.

Mobile nodes transmit and receive with the FMN 102 which provides thebest communications path at that given time; this FMN 102 is consideredto be the mobile node's parent at that time. As a mobile node travelsthrough the network its position relative to a given parent changes andtherefore the RF characteristics change. When the quality of the linkbetween the mobile node and its parent FMN 102 has degraded such that itis below a programmable threshold of acceptable operation, the mobilenode seeks another parent which can provide a higher qualitycommunication link. This results in the entry point of the voice anddata packets into the network changing with time.

In addition to mobility, the occasional removal of one or more FMNs 102from the network is an operational reality. This can occur due tomaintenance action, failure of a unit or loss of line of sight betweenunits due to obstructions or cave-in. Each of these scenarios can causea modification to the current route which packets are taking through thenetwork. Since the intelligent flood routing algorithm used by thecurrent invention does not attempt to establish any static orsemi-static routes for communication packets from a given source to agiven destination, it is able to immediately react to each of thesescenarios with minimal or no loss of data.

Flood routing is understood to those skilled in the art to be atechnique by which a router forwards packets received on all interfacesexcept the one on which said packet was received. This is known toartisans as a technique which can be used to add multicast support to amesh network. However, this technique can result in large amounts ofredundant traffic since there are many possibilities for circularrouting loops. The present invention eliminates circular loops bystoring a history of data packet sequence numbers and voice packettimestamps. As each data packet is forwarded, its sequence number isrecorded in memory along with a timestamp indicating the current systemtime. If another data packet is received with this same sequence numberbefore a programmable timeout period, this packet is discarded. Howeverif the sequence number of the data packet does not match any storedsequence number of recently forwarded packets, the packet is forwardedand the timestamp associated with that sequence number is replaced withthe current time.

A similar procedure is used for filtering duplicate voice packets,however timestamps are used instead of sequence numbers to eliminate thepossibility of forwarding a voice packet associated with a given voicestream which is significantly older than a previously forwarded voicepackets associated with the same voice stream. Each voice packetcontains two timestamps, one which indicates the time at which the firstvoice packet of the associated voice stream was transmitted into thenetwork and one which indicates the time at which this specific packetof the stream was transmitted into the network. As each voice packet isreceived by a FMN 102 it will only be forwarded if no other voice packetwas recently forwarded with the same voice stream origination time and apacket origination time which is greater than or equal to the packetorigination time in packet under consideration. In a preferredembodiment of this invention the definition of “recently” is controlledby a configurable timeout parameter.

6. Super-Frame Format

All transmissions on the mesh network are strictly time synchronized toincrease the likelihood of successful transmission of any given packet.Each FMN 102 utilizes a pair of bonded channels on which it willtransmit. FIG. 3 illustrates the super-frame timing used on both ofthese channels. The timing of the super-frames 305 on each channel issynchronized to prevent an FMN 102 from attempting to receive on onechannel while it is transmitting on another channel. The timing of thesuper-frame 305 for all the nodes in a cluster is synchronized with thetime master for that cluster providing the time reference.

In one embodiment of this invention each super-frame 305 is 60 ms induration and is subdivided into six 10 ms first level time slots. Thefirst five first level 10 ms time slots 310 are dedicated as first levelFMN-to-FMN time slots and the sixth 10 ms first level time slot 315 isdedicated as the first level Contention Access Period (CAP) time slot.The purpose of the first level FMN-to-FMN time slot 310 is to provide aguaranteed time period during which a FMN 102 can transmit networkpackets to its neighboring FMN(s) 102 and to any mobile units (MMRs 101or SMNs 103) which may be using it as their current parent.

The first level FMN-to-FMN time slot 310 is sub-divided into six secondlevel time slots as illustrated in FIG. 4. Each of these second leveltime slots has an assigned operation which will be executed by the FMNwhich is assigned the specific time slot. The second level Pre-guardtime slots 440 allows for clock drift between network components, theassigned FMN does not transmit or receive during this second level timeslot. The duration of the second level Pre-guard time slots 440 is fixedfor a given network based on the clock accuracy of the components withinthe network. The second level PA Ramp time slot 445 is a time slot setaside to allow the Power Amplifier (PA) component of the FMN to reachfull output power. The assigned FMN turns on its transmitter circuitryat the beginning of this second level time slot and then delays for theduration of the second level time slot without transmitting. Theduration of the second level PA Ramp time slot 445 is fixed for a givennetwork. The third second level time slot is the second level Primarytime slot 450. The assigned FMN uses the second level Primary time slot450 to transmit queued network packets to its listening neighbors.Typically, a single first level Concatenated Data Frame 1700, as shownin FIG. 17, is used to transfer all the network packets. The duration ofthe second level Primary time slot is variable depending on the numberof network frames in the assigned FMN's 102 outgoing queue. The secondlevel Primary time slot 450 is followed by an second level Idle timeslot 460 during which the FMN 102 can power down its transmitter toconserve power. The duration of the second level Idle time slot 460 isfixed for a given FMN 102; it may be adjusted during network deploymentto provide a method to trade-off network formation/re-formation timewith FMN power consumption. The second level Idle time slot 460 isfollowed by the second level Sync time slot 465 during which theassigned FMN 102 will transmit first level PHY frames 701 containingthird level Sync frames 1800. These Sync frames 1800 are used to aidscanning FMNs 102 or mobile nodes to find and synchronize with thenetwork. The number of Sync frames 1800 to be sent in a given secondlevel Sync time slot 465 may vary between subsequent super-framesdepending on the durations of the second level Idle time slot 460 andthe second level Primary time slot 450. The second level Post-guard timeslot 455 follows the second level Sync time slot 465. The FMN 102 usesthe second level Post-guard time slot 455 to turn off its transmitterand switch to receive mode for the next first level time slot 310 or315.

The purpose of the first level CAP time slot 315 is to provide anopportunity for other FMNs 102 to transmit Child Association requestframes to a potential parent FMN 102 and to provide an opportunity formobile nodes to transmit frames containing network packets into WMN 100.The exact format for first level CAP time slot 315 depends on whetherthat particular bonded channel is dedicated to voice or data. For agiven FMN 102, one of the bonded channels is designated as the datachannel due to the first level CAP time slot 315 being formatted intosecond level CAP data time slots 505, as illustrated in FIG. 5, and theother channel in the pair is designated as the voice channel due to thefirst level CAP time slot 315 being formatted into second level CAPvoice time slots 605, as illustrated in FIG. 6.

As FIG. 5 also illustrates, the second level CAP data time slots arefurther comprised of a third level TX On Guard time slot 510, a thirdlevel data Physical Layer (PHY) frame time slot 515, a third level dataIdle time slot 520 and a third level data TX Off Guard time slot 525.Third level data TX On Guard time slot 510 and third level data TX OffGuard time slot 525 instruct the radio transmitting in the CAP slot timeto turn its transmit circuitry on and off, respectively. Third leveldata Idle time slot 520 is the period of time after the transmittingradio has transmitted the last bit of the variable length third leveldata frame time slot 515 and before the beginning of third level data TXOff Guard time slot 525.

Similarly FIG. 6 illustrates, the second level CAP voice time slots 605are further comprised of a third level voice TX On Guard time slot 610,a third level voice Physical Layer (PHY) frame time slot 615, a thirdlevel voice Idle time slot 620 and a third level voice TX Off Guard timeslot 620. Third level voice TX On Guard voice time slot 610 and thirdlevel voice TX Off Guard time slot 625 instruct the radio transmittingin the CAP slot time to turn its transmit circuitry on and off,respectively [0034] FIG. 7 illustrates the general format of a firstlevel PHY frame 701. This frame format applies to both the third levelData Physical Layer (PHY) frame time slot 515 and the third level VoicePhysical Layer (PHY) frame time slot 615. A first level PHY frame 701 isfurther comprised of a second level PHY header frame 705 and a secondlevel MAC frame 710. The second level PHY header frame 705 furtherconsists of a third level Preamble frame 715, a third level Sync frame720 and a third level Length frame 725.

The third level Preamble frame 715 is encoded as a set of alternating 1and 0 bits. The purpose of this third level frame is to provide a meansfor receiving radios to reliably obtain bit synchronization on theincoming bit stream.

The third level Sync frame 720 consists of a unique bit pattern which ispreconfigured into all devices in WMN 100. This third level frame isused by a receiving radio to obtain slot synchronization.

The third level Length frame 725 indicates to the receiver the number ofbytes to expect in the second level MAC frame 710.

The second level MAC frame 710 contains several third level frames whichprovide control and error correction functions. These third level framesinclude a third level Frame Control frame 730, a third level SequenceNumber frame 735, a third level Destination Address frame 740, a thirdlevel Source Address frame 745, an third level Extended Header frame750, a third level MAC Payload frame 755 and a third level a cyclicredundancy check (CRC) frame 760.

The third level Frame Control frame 730 provides several fourth levelframes which inform the receiving radio of the purpose and format of theremainder of second level MAC frame 710. The format and purpose of thesefourth level frames are discussed in a subsequent section.

Third level Sequence Number frame 735 allows the acknowledgement ofindividual MAC packets and the filtering of duplicate packets. The valueof this third level frame is set by the transmitter of the packet.Whenever a unicast acknowledgement is sent to indicate the status of thereception of this packet the value of the third level Sequence Numberframe 735 in the Acknowledgement is set to this value.

Third level destination address frame 740 specifies the network addressof the intended recipient of this packet. The length of this third levelframe is determined by fourth level Destination Mode frame 845, shown inFIG. 8, of third level frame control frame 730. In the preferredembodiment of this invention certain Destination Address values arereserved to indicate a packet is a broadcast packet and should thereforebe processed by all receiving nodes.

Third level Source Address frame 745 specifies the network address ofthe transmitting unit. The length of this third level frame isdetermined by fourth level Source Mode frame 855, shown in FIG. 8, ofthird level Frame Control frame 730.

The purpose of third level Extended Header(s) frame 750 is to provide amechanism by which the sender can dynamically expand the MAC header withadditional network information when needed. The format of this thirdlevel frame is described in a subsequent section.

The purpose and content of third level MAC Payload frame 755 is contextdependent. The types of MAC packets which are supported on the WMN 100are described in a subsequent section.

Third level CRC frame 760 provides the receiver with a method fordetecting bits errors which may have occurred in the demodulation of thedata bits in other third level frames 730, 735, 740, 745, 750 and 755.This third level frame is 16 bits in length and is calculated using thestandard CCITT CRC16 parameters.

Frame Control Field

The third level Frame Control frame 730 consists of several fourth levelframes which inform the receiving radio of the purpose and format of theremainder of the second level MAC frame 710. FIG. 8 illustrates theformat of the third level Frame Control frame 730. The fourth levelframes within the third level Frame Control frame are shown in FIG. 8and comprise the fourth level Frame Type frame 805, the fourth levelSecurity Enabled frame 810, the fourth level Frame Pending frame 815,the fourth level ACK Request frame 820, the fourth level Intra-personalarea network (Intra-PAN) frame 825, the fourth level Extended Headerindication flag frame 830, the fourth level Scan frame 835, the fourthlevel Retry frame 840, the fourth level Destination Mode frame 845, thefourth level Power Control frame 850 and the fourth level Source Modeframe 855.

The fourth level Frame Type frame 805 indicates the purpose of thissecond level MAC frame 701 and therefore indicates the format of thethird level MAC Payload frame 755. The three fourth level MAC frametypes used on this system are Single Data Frames, Concatenated DataFrames and Sync frames.

The fourth level Security Enabled frame 810 indicates whether or not MAClayer security is enabled.

The fourth level Frame Pending frame 815 indicates whether the sendingunit has additional frames to send to the same destination address.

The fourth level ACK Request frame 820 indicates whether the sendingunit is requesting a MAC layer acknowledgement of this frame.

The fourth level Intra-PAN frame 825 is reserved for future intra-PANcommunications.

The fourth level Extended Header indication flag frame 830 is a flagwhich, when set to true, indicates whether or not one or more fourthlevel extended header frames follows the third level Source Addressframe.

The fourth level Scan Notify frame 835 indicates whether or not thetransmitter will be performing a scan operation in the next time slot orwill be performing a normal transmission in the time slot.

The fourth level Retry frame 840 indicates whether or not the firstlevel frame is a first transmission of the contained information or aretry of the transmission of the information.

The fourth level Destination Mode frame 845 indicates number of bits inthe third level Destination Address frame 740.

The fourth level Power Control frame 850 is used to indicate the powerlevel at which the transmitter is transmitting the packet.

The fourth level Source Mode frame 855 indicates the number of bits inthe third level Source Address frame 745.

Extended Headers

The third level Extended Header frame 750 of the second level MAC frame710 may consist of zero or more fourth level Extended Header frames 905as illustrated in FIG. 9. The presence or absence of the first fourthlevel Extended Header frame 905 is indicated by fourth level ExtendedHeader indication frame 830 of third level Frame Control frame 730. Thepresence or absence of each subsequent fourth level Extended Header 905is indicated by the fifth level Next Extended Header frame 1005 in theheader of the preceding fourth level Extended Header 905 frame. Thereare four different types of Extended Header frames 905, each of whichhas a different format.

As illustrated in FIG. 10, each fourth level Extended Header frame 905consists of four generic elements. These elements are a fifth level NextExtended Header frame 1005, a fifth level Extended Header Length frame1010, a fifth level Extended Header Type frame 1015 and a fifth levelExtended Header Data frame 1020.

The fifth level Next Extended Header frame 1005 indicates the presenceor absence of an additional fourth level Extended Header frame 905following this fourth level Extended Header frame 905.

The fifth level Extended Header Length field 1010 indicates the numberof octets in the fifth level Extended Header Data frame 1020.

The fifth level Extended Header Type field 1015 indicates the purpose ofthis particular fourth level Extended Header frame 905 and thesubsequent format of the fifth level Extended Header Data frame 1020.There are five possible types of fourth level Extended Header frameswhich are Slot Info headers, Piggyback ACK headers, Piggyback Grantheaders, Power Control headers and Future Grant headers.

The format of the first type of fourth level Extended Header frame 905incorporates a fifth level Slot Info Extended Header frame 1100, asillustrated in FIG. 11. The contents of the fifth level Slot InfoExtended Header Data frame 1100 consists of six sixth level frames: theACK Map frame 1105, the Channel frame 1110, the Cycle Slot #/FosterRotation frame 1115, the Long Slot Number frame 1120, the Time Masterframe 1125 and the Time Hops frame 1130.

The sixth level ACK Map frame 1105 is a bit mapped frame used toacknowledge multi-cast packets which have been received by the FMN 102transmitting the Slot Info Extended Header.

The sixth level Channel frame 1110 indicates the logical channel onwhich this first level frame is being transmitted. This value, incombination with the slot and super-frame numbers can be used tosynchronize to the transmitting unit hopping sequence if frequencyhopping is being used.

The sixth level Cycle Slot #/Foster Rotation frame 1115 consists ofthree seventh level frames as illustrated in FIG. 12. The first seventhlevel frame is the parent slot number frame 1205 which advertiseswhether the transmitting unit is a fostering MMR 101 or an FMN 102 andif it is the latter, this field indicates the slot number of thefostering MMRs 101 parent FMN 102. The second seventh level frame is theFoster Rotation Number frame 1210 which advertises the future positionof the voice and data CAP slots for a MMR which is being fostered. Thefinal seventh level frame is the Slot Rotation Cycle frame 1215 which isused by a fostering MMR 101 to advertise which slot rotation schedule itis currently employing.

The sixth level Long Slot Number frame 1120 of a Slot Info ExtendedHeader indicates the current value of the 16 bit slot number.

The sixth level Time Master frame 1125 of a Slot Info Extended Headerindicates the ID of time master of the cluster to which the transmittingunit is a member.

The sixth level Time Hops frame 1130 indicates the number of hops to theTime Master of the cluster.

FIG. 13 illustrates the format of the second type of fourth levelExtended Header frame 905. This type of frame incorporates a fifth levelPiggyback ACK Extended Header Data frame 1300 which is used by thetransmitting unit to acknowledge a previously received unicast packet. Asixth level Sequence Number frame 1305 indicates the sequence number ofthe packet being acknowledged. A sixth level Address frame 1310indicates the Source ID which was received in the packet beingacknowledged. The sixth level receive signal strength indication (RSSI)frame 1315 indicates the receive signal strength at which the packetbeing acknowledged was received.

FIG. 14 illustrates the format of the third type of fourth levelExtended Header frame 905. This type of frame incorporates a fifth levelPiggyback Grant Extended Header frame 1400 which is used by thetransmitting unit to indicate which nodes are allowed to transmit in thenext first level CAP time slot 315. This arrangement provides a methodby which bandwidth can be reserved for a unit which has multiple packetsto send. Each of the four sixth level Address frames 1405, 1410, 1415and 1420 will specify either a unicast address if the correspondingsecond level upstream time slot is reserved for a unicast transmissionfrom a particular unit or to the special broadcast address if thecorresponding second level CAP time slot is to be used as a CAP slot. Inalternative embodiments, there may be more than four sixth level Addressframes.

The fourth type of fourth level Extended Header frame 905 incorporates afifth level Power Control Extended header frame which is notillustrated. This type of frame is used to communicate the current powersetting of the transmitter. This is necessary since the power controlalgorithm may cause a unit to transmit at less than its nominal powersetting and this information is needed to allow the receiving units tonormalize the received signal strength readings associated with thisunit. Since the receive power levels are used for positiontriangulation.

FIG. 15 illustrates the format of the fifth type of fourth levelExtended Header frame 905. This type of frame incorporates a fifth levelFuture Grant Extended Header frame 1500 which is used to reserve secondlevel CAP time slots 315 for the upstream two slots in the future. Itsprimary purpose is to prevent an FMN 102 from transmitting in the nextsecond level CAP time slot and missing its guaranteed grant coming up inthe second level time slot after that. Each of the four sixth levelAddress frames 1505, 1510, 1515 and 1520 will specify either a unicastaddress if the corresponding second level CAP time slot is reserved fora unicast transmission from a particular unit or to the specialbroadcast address if the corresponding second level CAP time slot is tobe used as a CAP slot. In alternative embodiments, there may be morethan four sixth level Address frames.

MAC Packet Types

There are three possible formats for the third level MAC payload frame755 used on WMN 100. As mentioned above, the specific type of MAC packetis indicated in the fourth level Frame Type frame 805. These three thirdlevel frame types are Single Data Frames, Concatenated Data Frames andSync Frames.

FIG. 16 illustrates the format of a first level Single Data frame 1600.The purpose of a first level Single Data frame 1600 is to transfer oneand only one network packet. For this type of frame the third level MACPayload frame 755 consists entirely of a single fourth level networkpacket frame 1605. The third level Length field 725 will indicate thelength of the fourth level network packet frame 1605. The other thirdlevel fields of the first level Single Data frame 1600 will be used asdescribed in the preceding sections.

FIG. 17 illustrates the format of a first level Concatenated Data frame1700. This frame type is used to transfer zero, one or more fourth levelnetwork packet frames 1605 between units. For this type of frame, thethird level MAC Payload frame 755 consists of zero, one or moreLength/Network Packet pairs. Each of these pairs will consist of afourth level Length frame 1705 and a variable length fourth levelNetwork Packet frame 1605 The fourth level Length frame 1705 indicatesthe number of octets in the corresponding fourth level Network Packetframe 1605. The fourth level Network Packet frame 1605 contains theactual application layer information being transferred. The third levelPHY Length frame 725 will indicate the number of octets in all of thefourth level Length/Network Packet pairs. The other third level framesof this type of first level packet frame are used as described in thepreceding sections.

FIG. 18 illustrates the format of first level Sync frame 1800. This typeof frame may be sent during a first level FMN-to-FMN time slot 310 tofacilitate adjacent FMNs 102 and mobile nodes in finding the network.The third level MAC Payload frame 755 for this first level frame type1800 consists of a fourth level Time Master frame 1805, a fourth levelSlot Number frame 1810 and a fourth level Channel Number frame 1815. Thevalue of the fourth level Time Master frame 1805 is set to the networkID of the current time master of the transmitting unit. The value of thefourth level Slot Number frame 1810 is set to the current slot numberfor the cluster to which the transmitting unit belongs. The value of thefourth level Channel Number frame 1815 is set to the logical channelnumber on which the SYNC frame is being transmitted.

In alternative embodiments, more than one of any of the disclosed typesof time slots and frames may be incorporated into the communicationsprotocol formed with this invention.

In an emergency situation the need for reliable communications isparamount. For example, in a hazardous environment, such as underground,direct communications between two points is often made unreliable orimpossible by destroyed infrastructure and/or blockage of line-of-sightby equipment and/or debris. By design, this invention creates a methodby which the ad hoc mesh nodes automatically form and re-form inclusters to provide reliable network communications. This characteristicfacilitates the natural creation of clusters of communication aroundFMN's 102 to provide an infrastructure and provides a method by whichisolated pockets (clusters) of FMN's 102 can quickly reconnect with themain infrastructure. This invention further creates a protocol thatprovides a reliable wireless network formed by ad hoc mesh nodes. Thecommunication protocol supports the creation and maintenance of areliable network 100 including fixed and mobile nodes. This protocolprovides methods by which mobile devices can communicate with othermobile devices and with Network Operations Center 105 while roamingfreely through the network formed by the Fixed Mesh Nodes (FMN) 102. Theprotocol supports voice, data and text communications in emergency andnon-emergency modes. In addition this protocol provides methods by whicheach infrastructure node and mobile node can be monitored and managed atremote Network Operations Center 105.

While the preferred embodiments of the present invention have beenillustrated and described, it will be understood by those skilled in theart that various changes and modifications may be made, and equivalentsmay be substituted for elements thereof without departing from the truescope of the present invention. In addition, many modifications may bemade to adapt the teaching of the present invention to a particularsituation without departing from its central scope. Therefore it isintended that the present invention not be limited to the particularembodiments disclosed as the best mode contemplated for carrying out thepresent invention, but that the present invention include allembodiments falling within the scope of the appended claims.

What is claimed is:
 1. A method for implementing a communicationsnetwork protocol suitable for reliable voice and data communications inan underground, industrial, or hazardous area comprising: providing awireless mesh network (WMN) comprising ad hoc mesh nodes thatautomatically form and re-form in clusters to provide wireless networkcommunications to support voice, data, text and network service forpersonnel working in the hazardous area; wherein the wireless meshnetwork (WMN) comprises fixed mesh nodes (FMNs) and mobile nodes andeach FMN provides creation and maintenance of the WMN by coordinatingindividual clusters within the WMN and routing data through the WMNbetween mobile nodes and a Gateway node for access to and/or from aremote Network Operations Center; establishing dedicated bandwidthtransmission opportunities for each FMN in a given cluster to forwardpackets to a neighbor node in the cluster and to establishcontention-based transmission opportunities for the FMNs and the mobilenodes to join the cluster; establishing contention-free transmissionopportunities by providing a two-way medium for each node with a bondedfrequency pair and associated contention-free time slot to provide aguaranteed time period during which an FMN transmits network packets toneighboring FMN(s) and to mobile units using the FMN as a parent to,wherein format for the contention-free time slot depends on voice ordata dedication; establishing contention-based transmissionopportunities to join the cluster by providing a two-way medium for eachnode with a bonded frequency pair and associated contention-based timeslot, wherein format for the contention-based time slot depends on voiceor data dedication; wherein distributing application layer packets isperformed with high reliability and low latency to maintain reliablevoice and data communications with mobile nodes carried by personnel andfixed or mobile sensors within the hazardous area and also with remoteoperation; providing an intelligent flood routing technique with dynamicpacket routing to ensure that at least one mobile node can seamlesslyroam within the ad hoc mesh network; wherein the intelligent floodrouting technique immediately reacts to a mobile node roaming freelythrough the ad hoc mesh network and to removal of one or more FMNs withminimal or no loss of data since it does not establish static orsemi-static routes for communication packets from a given source to agiven destination; wherein the intelligent flood routing techniqueeliminates circular loops and duplicate voice packets by storing ahistory of data packet sequence numbers and voice packet timestamps toremove large amounts of redundant traffic associated with flood routingwherein each FMN and each mobile node contains a communications networkprotocol for automatically forming an association with one or moreneighbor FMNs, and wherein the ad hoc mesh network is based oncooperative negotiation and a dynamic parent-child relationship betweennodes for determination of network time synchronization without apre-determined time master, discovery and merging of adjacent ad hocmesh networks, and routing techniques for voice, data and network statuspackets which react to network topology changes, such that when acommunications link in the ad hoc mesh network degrades or fails,another FMN is automatically designated; wherein when quality of a linkbetween a mobile node and a parent FMN has degraded such that it isbelow a programmable threshold of acceptable operation, the mobile nodeseeks another parent which can provide a higher quality communicationlink; wherein each fixed node and mobile node is monitored and managedat the remote Network Operations Center for dispatch, remotesupervision, and tracking of personnel, as well as, monitoring, assetcontrol, and management of wireless sensors and equipment; wherein thead hoc mesh network comprises at least one node cluster with (i) aplurality of peer-to-peer fixed mesh nodes (FMNs), one of which is atime master node, and (ii) at least one mobile mesh radio node;establishing a super-frame time interval for all nodes in a cluster,wherein the super-frame time interval is time synchronized with the timemaster node for the cluster based on node ID ranking, and wherein childnodes will synchronize to their respective parent nodes' slot timingthus inheriting the time master's timing with some offset due topropagation delay: wherein when a communications link in the ad hoc meshnetwork degrades or fails, another FMN is automatically designated astime master node based on node ID ranking; establishing at least twotime slots in a primary channel and secondary channel within thesuper-frame time interval; assigning at least one of the time slots as acontention-based time slot for transmitting data to form parent-childassociations to join the ad hoc mesh network by one or more of theplurality of FMNs and/or the at least one mobile mesh radio node;assigning at least one of the time slots as an FMN to FMNcontention-free time slot for transmitting network packets from one ormore of the FMNs to a neighboring FMN that will use a transceiver totune to frequencies associated with a transmitting FMN and receivepackets and/or to any mobile mesh radio node associated with an FMN thatwill use a transceiver to tune to frequencies associated with atransmitting FMN and receive packets; wherein for an FMN-to-FMN timeslot not assigned to a neighbor, a node will use both transceivers toscan for other clusters to provide an improved time metric; and whereineach FMN will periodically puncture its own FMN-to-FMN time slot as wellas a neighbors' assigned time slot(s) and contention access time slot toperform a scan operation for other clusters to provide an improved timemetric.
 2. The method of claim 1, wherein each of the at least one FMNto FMN time slots creates a reliable wireless digital communication toone or more neighbor nodes consisting of: at least one pre-guard timeslot to allow for clock drift between nodes; at least one poweramplifier ramp time slot to allow the FMN to reach full output power; atleast one primary time slot to transmit network packets to one or morelistening neighbors; at least one idle time slot for FMN power down ofthe FMN's transmitter to conserve power; at least one sync time slot toaid scanning FMNs or mobile nodes to find and synchronize with the adhoc mesh network; and at least one post-guard time slot to turn off theFMN's transmitter and switch to receive mode.
 3. The method of claim 1,wherein each fixed mesh node (FMN) transmits and receives over a pair ofbonded, time-synchronized RF channels, one of which is designated as adigital voice channel and a second of which is designated as a digitaldata channel to provide quality of service mechanism and prevent an FMNfrom attempting to receive on one channel while the FMN is transmittingon the second channel.
 4. A method for implementing a wireless digitalcommunications network protocol for critical voice, data and real-timemonitoring of conditions and equipment in an underground hazardousenvironment, the method comprising: providing an ad hoc mesh networkwith a reliable two-way medium based on cooperative negotiation forestablishing dedicated transmission opportunities to forward packets inan efficient manner as well as contention-based transmissionopportunities to join; wherein the ad hoc mesh network comprises atleast one node cluster having a plurality of peer-to-peer fixed meshnodes (FMN) and at least one mobile mesh radio node wherein each FMN andthe at least one mobile mesh radio node contains the said communicationsnetwork protocol to automatically form an association with one or moreneighbor FMN's; providing an intelligent de-centralized flood routingtechnique with dynamic routing to ensure that the at least one mobilemesh radio node can seamlessly roam throughout the ad hoc mesh network;providing uni-cast and multi-cast voice, text and data packettransmissions; providing a combined wireless and wired emergencycommunications system, including the ad hoc mesh network adapted for usewith the communications network protocol; establishing at least onesuper-frame time interval within the communications network protocol,each of which is of equal duration and each of which is timesynchronized with a designated FMN time master for each cluster using adynamic parent-child relationship among the FMNs that is notpre-determined; establishing at least two time slots within each saidsuper-frame time interval; assigning at least one of said at least twotime slots as a contention access period (CAP) time slot fortransmitting data to form associations into the ad hoc mesh network byone or more of the plurality of FMN's and/or the at least one mobilemesh radio node; assigning at least one of said at least two time slotsas an FMN to FMN contention-free time slot for transmitting networkpackets from one or more of the plurality of FMN's to neighboring FMN'sof the plurality of FMN's and/or to any mobile mesh radio nodes withwhich the FMN is associated; wherein each of the at least one CAP timeslots is formatted into at least one CAP data time slot or at least oneCAP voice time slot to receive packets from transmitting mobile meshradio nodes or other FMNs which are attempting to join the at least onenode cluster, or scan for other node clusters wherein each CAP time slotfurther comprises: at least one data TX on guard time slot for a radiotransmitting in the CAP time slot to turn the radio's transmit circuitryon; at least one data physical layer (PHY) frame time slot to transmitnetwork packets to one or more listening neighbors; at least one voicePHY frame time slot; at least one data idle time slot after thetransmitting radio has transmitted a last bit of variable length data;and at least one data TX off time slot for a radio transmitting in theCAP time slot to turn the radio's transmit circuitry off.
 5. The methodof claim 4, wherein each said data PHY frame time slots and each saidvoice PHY frame time slots further comprises: at least one PHY headerframe for bit synchronization of the data packet; and at least one mediaaccess control (MAC) frame to provide control and error correctionfunctions.
 6. The method of claim 5, wherein each said PHY header framefurther comprises: at least one preamble frame encoded as a set ofalternating 1 and 0 bits to provide a means for receiving radios toreliably obtain bit synchronization on an incoming bit stream; at leastone sync frame consisting of a unique bit pattern which is preconfiguredinto all devices which is used by a receiving radio to obtain slotsynchronization; and at least one length frame which indicates to areceiver a number of bytes to expect in the MAC frame.
 7. The method ofclaim 5, wherein each said MAC frame further comprises: at least oneframe control frame which informs the receiving radio of a purpose andformat of a remainder of the MAC frame; at least one sequence numberframe which allows for acknowledgement of individual MAC packets and forfiltering of duplicate packets where the sequence number frame is set bya transmitter of the packet; at least one destination address frame thatspecifies a network address of an intended recipient of the packet; atleast one source address frame that specifies a network address of atransmitting unit; at least one extended header frame to provide amechanism by which a sender can dynamically expand a MAC header withadditional network information when needed; at least one MAC payloadframe which is context dependent; and at least one cyclic redundancycheck (CRC) frame which provides the receiver with a method fordetecting bits errors that occurred in demodulation of data bits inother frames.
 8. The method of claim 7, wherein each said frame controlframe further comprises: at least one MAC frame type frame thatindicates a purpose of the MAC frame and a format of the MAC payloadframe, wherein MAC frame types are selected from single data frames,concatenated data frames, and sync frames; at least one security enabledframe which indicates whether or not MAC layer security is enabled; atleast one frame pending frame which indicates whether a sending unit hasadditional frames to send to the same destination address; at least oneacknowledge (ACK) request frame which indicates whether the sending unitis requesting a MAC layer acknowledgement of this frame; at least oneintra-PAN frame which is reserved for future intra-PAN communications;at least one extended header indication flag frame which, when set totrue, indicates whether or not one or more extended header framesfollows the Source Address frame; at least one scan notify frame whichindicates whether or not the transmitter will be performing a scanoperation in the next time slot or will be performing a normaltransmission in the next time slot; at least one retry frame whichindicates whether or not the frame is a first transmission or asubsequent transmission; at least one destination mode frame whichindicates a number of bits in the Destination Address frame; at leastone power control frame indicates a power level at which the transmitteris transmitting the packet; and at least one source mode frame whichindicates a number of bits in the Source Address frame.
 9. The method ofclaim 8, wherein if a flag of said extended header indication flag frameis set to true, each said extended header frame further comprises atleast one extended header frame type selected from the group consistingof: slot info header frame, piggyback ACK header frame which is used bythe transmitting unit to acknowledge a previously received unicastpacket, piggyback grant header frame which is used by the transmittingunit to indicate which nodes are allowed to transmit in a next firstlevel CAP time slot, power control header frame which is used tocommunicate a current power setting of the transmitter, and future grantheader frame which is used to reserve CAP time slots for the upstreamtwo slots in the future.
 10. The method of claim 9, wherein each saidslot info header frame further comprises: at least one ACK map frameused to acknowledge multicast packets which have been received by theFMN transmitting a Slot Info Extended Header; at least one channel framewhich indicates a logical channel on which the frame is beingtransmitted, the at least one channel frame, in combination with slotand super-frame numbers, can be used to synchronize to a transmittingunit hopping sequence if frequency hopping is used; at least one cycleslot number or foster rotation frame consisting of a parent slot numberframe, a foster rotation number frame, and a slot rotation cycle frame;at least one long slot number frame indicating a current value of a 16bit slot number; at least one time master frame indicating an ID of thetime master FMN of the node cluster to which the transmitting unit is amember; and at least one time hops frame indicating a number of hops tothe time master of the node cluster.
 11. The method of claim 10, whereineach cycle slot number or foster rotation frame further comprises: atleast one parent slot number frame which advertises whether thetransmitting unit is a fostering mobile mesh radio node or an FMN; atleast one foster rotation number frame which advertises a futureposition of the voice and data CAP time slots for a mobile mesh radionode which is being fostered; and at least one cycle slot rotation cycleframe which is used by a fostering mobile mesh radio node to advertisewhich slot rotation schedule the fostering mobile mesh radio node iscurrently employing.
 12. The method of claim 9, wherein each saidpiggyback ACK header data frame further comprises: at least one sequencenumber frame indicating a sequence number of a packet beingacknowledged; at least one address frame indicating a Source ID whichwas received in the packet being acknowledged; and at least one receivedsignal strength indication (RSSI) frame with a received signal strengthat which the packet being acknowledged was received.
 13. The method ofclaim 9, wherein each piggyback grant header frame is configured toreserve bandwidth for any one of the nodes having multiple packets tosend and wherein each piggyback grant header frame further comprises atleast four address frames to specify either a unicast address if acorresponding upstream time slot is reserved for a unicast transmissionor a special broadcast address if a corresponding upstream time slot isto be used as a CAP slot.
 14. The method of claim 9, wherein each futuregrant header frame is configured to prevent an FMN from transmitting ina next CAP time slot and missing the FMN's guaranteed grant coming up ina time slot after that and wherein each future grant header framefurther comprises at least four address frames to specify either aunicast address if a corresponding time slot is reserved for a unicasttransmission or a special broadcast address if the corresponding timeslot is to be used as a CAP slot.
 15. The method of claim 7, whereineach said MAC payload frame is one type selected from the groupconsisting of single data frame type, concatenated data frame type, andsync frame type where: the single data frame type is used to transferone and only one network packet between units; the concatenated dataframe type is used to transfer zero, one or more network packet framesbetween units; and the sync frame type is sent during an FMN-to-FMN timeslot to facilitate adjacent FMNs and mobile mesh radio nodes in findingthe ad hoc mesh network.
 16. The method of claim 15, wherein said singledata frame type of said MAC payload frame comprises a single networkpacket.
 17. The method of claim 15, wherein said concatenated data frametype of said MAC payload frame further comprises: at least one lengthframe indicating a number of octets in a corresponding network packetframe; and at least one network packet frame containing an actualapplication layer information being transferred.
 18. The method of claim15, wherein said sync frame type of said MAC payload frame furthercomprises: at least one time master frame which is set to a network IDof a current time master FMN of the transmitting unit; at least one slotnumber frame which is set to a current slot number for a cluster towhich the transmitting unit belongs; and at least one channel numberframe which is set to a logical channel number on which the sync frametype is being transmitted.
 19. The method of claim 1, further comprisingof a periodic scanning operation to discover active nodes of anothernode cluster having overlapping time slots to obtain differentassociations between nodes to re-form the at least one node cluster suchthat individual nodes change from one node cluster to another nodecluster and wherein the periodic scanning operation is performed duringunused time slots, or by capturing a time slot of one of the at leastone fixed or at least one mobile mesh radio nodes and replacing theoperation otherwise assigned to a captured time slot with the periodicscanning operation.
 20. The method of claim 1, further comprising ofseamless data packet routing within the ad hoc mesh network, each packethaving a packet header, with the seamless packet routing comprising of:analyzing each of the packet headers including timestamp and sequencenumber; recording a history of packet sequence numbers and packettimestamps; determining based on the packet header whether to forwardthe packet to adjacent nodes; discarding packets with the same sequencenumber before a programmable timeout period to eliminate circular loopsand duplicate packets; and flood routing non-redundant packets toadjacent nodes in the ad hoc mesh network.
 21. The method of claim 1,further comprising of seamless roaming by one or more of the at leastone mobile mesh radio nodes by measuring quality of a channel linkbetween the mobile mesh radio node and a parent FMN to which the mobilemesh radio node is connected as compared with quality of availablechannel link with other FMNs, such that the mobile mesh radio nodeautomatically selects and connects to a different FMN having a betterquality channel link available as the mobile mesh radio node travelsthrough the ad hoc mesh network.
 22. A method for implementing acommunications network protocol comprising: providing a combinedwireless and wired emergency communications system with an ad hoc meshnetwork with two-way medium for establishing contention-free dedicatedtransmission opportunities to forward packets as well ascontention-based transmission opportunities to join; wherein the ad hocmesh network comprises at least one node cluster with (i) a plurality ofpeer-to-peer fixed mesh nodes (FMNs), one of which is a time masternode, and (ii) at least one mobile mesh radio node; wherein each FMN andeach mobile mesh radio node contains a communications network protocolfor automatically forming an association with one or more neighbor FMNs,and wherein the ad hoc mesh network is based on cooperative negotiationand a dynamic parent-child relationship between nodes, such that when acommunications link in the ad hoc mesh network degrades or fails,another FMN is automatically designated as the time master node;providing an intelligent flood routing technique with dynamic packetrouting to ensure that the at least one mobile mesh radio node canseamlessly roam throughout the ad hoc mesh network formed by the FMNs;establishing a super-frame time interval for all nodes in a cluster,wherein the super-frame time interval is time synchronized with the timemaster node for the cluster; establishing at least two time slots withinthe super-frame time interval; assigning at least one of the time slotsas a contention-based time slot for transmitting data to formassociations to join the ad hoc mesh network by one or more of theplurality of FMNs and/or the at least one mobile mesh radio node; andassigning at least one of the time slots as an FMN to FMNcontention-free time slot for transmitting network packets from one ormore of the FMNs to a neighboring FMN and/or to any mobile mesh radionode with which an FMN is associated; wherein each of the at least oneFMN to FMN time slots creates a reliable wireless digital communicationto one or more neighbor nodes consisting of: at least one pre-guard timeslot to allow for clock drift between nodes; at least one poweramplifier ramp time slot to allow the FMN to reach full output power; atleast one primary time slot to transmit network packets to its listeningneighbors; at least one idle time slot for FMN power down of itstransmitter to conserve power; at least one sync time slot to aidscanning FMNs or mobile nodes to find and synchronize with the ad hocmesh network; and at least one post-guard time slot to turn off itstransmitter and switch to receive mode.